Oxygen regulators, medical type

I'm looking for an inexpensive oxygen system for occasional flights up to 18,000 feet MSL. It seems easy to get a used medical type bottle with a regulator that includes a flow restriction built in. You can select, e.g., a 1 lpm flow rate right on the regulator. But, in a glider, you won't be able to reach this control when it is mounted behind the seat. My question is: with this type of regulator, if you add a flow valve and meter downstream, between that regulator and a cannula, and you open the flow on the medical regulator, but shut the added flow valve (unless and until you reach an altitude high enough to need oxygen), will the flow restrictor on the regulator protect the low-pressure hoses from excessive pressure, or will pressure build up enough to pop the hoses?

A side question is how to re-fill such a bottle.

On Thursday, November 5, 2015 at 6:19:34 PM UTC-5, wrote:
I'm looking for an inexpensive oxygen system for occasional flights up to 18,000 feet MSL. It seems easy to get a used medical type bottle with a regulator that includes a flow restriction built in. You can select, e.g., a 1 lpm flow rate right on the regulator. But, in a glider, you won't be able to reach this control when it is mounted behind the seat. My question is: with this type of regulator, if you add a flow valve and meter downstream, between that regulator and a cannula, and you open the flow on the medical regulator, but shut the added flow valve (unless and until you reach an altitude high enough to need oxygen), will the flow restrictor on the regulator protect the low-pressure hoses from excessive pressure, or will pressure build up enough to pop the hoses?

A side question is how to re-fill such a bottle.

Sounds a bit like do it yourself brain surgery.
Don't be a fool, buy proper equipment. This is a life support system.
UH

On Thursday, November 5, 2015 at 5:19:34 PM UTC-6, wrote:
I'm looking for an inexpensive oxygen system for occasional flights up to 18,000 feet MSL. It seems easy to get a used medical type bottle with a regulator that includes a flow restriction built in. You can select, e.g., a 1 lpm flow rate right on the regulator. But, in a glider, you won't be able to reach this control when it is mounted behind the seat. My question is: with this type of regulator, if you add a flow valve and meter downstream, between that regulator and a cannula, and you open the flow on the medical regulator, but shut the added flow valve (unless and until you reach an altitude high enough to need oxygen), will the flow restrictor on the regulator protect the low-pressure hoses from excessive pressure, or will pressure build up enough to pop the hoses?

A side question is how to re-fill such a bottle.

I agree with uncl..., would you scuba dive with cobbled together equipment.

The short answer is, yes, the pressure will most probably build to a point that the hoses and/or connections will fail with the system blocked downstream of a simple flow restricting orifice.

Most regulators for aviation use (i.e. Mountain High E & S) have an internal diaphragm that shuts off flow when the downstream pressure equals the upstream pressure. I highly recommend regulators with this feature, for obvious reasons.

At the same time, I can also recognize the (cheaper) alternatives IF YOU DO NOT SHUT OFF THE FLOW COMPLETELY. The pressure will not increase to the point that mechanical components (tubes and connectors) are likely to fail. However, don't forget to turn the flow rate up when you salvage your flight with a low save and are feeling like a superhero for getting back above 12,000. I have heard more than one badly performed bit of karaoke on the radio when somebody forgot to adjust the O2 flow at altitude.

Pressure in the cylinder is often at 2,200 psi or more (using Aviators Breathing Oxygen from a reputable supplier) but nominal pressure is generally from 1,800 to 2,000 psi on a full tank. Most regulators (orifice type) only reduce the pressure to 15-100 psi, and do not shut the flow off when this pressure is reached, allowing the downstream pressure to eventually try to match the much higher cylinder pressure, resulting in failure of the downstream components. Don't worry, your head won't explode, but you might freak out at the sudden pop and hissing noise when it happens. And then the cylinder empties at an enthusiastic rate.

Please extinguish your cigarettes when this happens, or your whole airplane might explode. or at least turn into a merry little fireball.

Regulators with a diaphragm will regulate the pressure to the optimum level needed to operate the delivery mechanism, whether it is an electronic demand system (MH EDS) or a simple flow meter. Medical regulators are not capable of doing anything but reducing pressure to a manageable rate suitable for a constant flow rate with no change in altitude (and therefore increased O2 requirement).

In a nutshell- buy the best stuff for the application (aviation). If you get cheap crap because you are, well, cheap, don't shut off the flow entirely..

It is just your life, so go as cheap as you think it is worth. Remember that Oxygen refills are generally pretty cheap, and unless you have an extremely small cylinder, saving O2 by shutting the flow down doesn't save much in the way of time vs. altitude. Especially when you have to constantly remind yourself to turn it up at altitude or turn it down when the "houses get bigger." The automatic demand systems (M H E&S) take that out of the equation, so you can just concentrate on flying as best you can.

(I have been giving this lecture to hang glider and sailplane pilots since 1988, when I started selling 02 systems. I am also a dealer for M H E&S. In 2014, I got 147 hours of airtime. I was on 02 for 136 of them.)

Have fun, but don't be stupid. Just because you do not use 02 very often does not mean that you should go cheap. Oxygen is fuel for your brain.

Thanks for the advice, Mark. I'd love an EDS system. But here in the East we rarely go high enough to need oxygen, it seems that spending $1000 on a system is overkill for use once a year or so. Also, we have very few convenient places around here to refill, other than at "wave camp".

Do those medical regulators not have a diaphragm? You'd think that's necessary, in order to shut off (at least mostly) the flow coming from the high pressure cylinder? I was guessing they have a diaphragm-based pressure reduction followed by an orifice to set the flow rate, but I may be wrong. And perhaps even the diaphragm system would have some leakage through the high pressure side valve even when it's supposedly shut because the diaphragm senses that the output pressure is high. Then again, these regulators have an "off" position, on the same knob as the non-zero flow rates. If that is simply a zero-size orifice, wouldn't the pressure then build up dangerously in the low-pressure side of that device?

From what I know about medical regulators, (admittedly, not much, as they aren't aviation oriented systems) is that they are basically pressure reducing constant flow systems not designed to handle a shutoff at the nose (and brain) end.

Some may have the capability to regulate pressure on both sides of the orifice, but do you really want to bet on it? Do some research. I personally think that using a medical system in an aviation environment would be kind of like trusting a dentist to pilot an airliner.

Your choice. Spending $1000 (or less for some actual aviation systems) is not that much, unless you value your life and aircraft at a lesser amount.

If the regulating device has an "off" position, I would assume that is designed to actually reduce the flow to zero with no build up of high pressure that may compromise the system. But, as I said, I don't much care about what they do in a medical environment. I fly airplanes, and hopefully won't have to worry about sucking O2 in a hospital bed for some time. Until then, I will pick an aviation system.

It is possible that the medical system you refer to has lines and connectors between the cylinder and the flow regulator designed to handle the pressures, but I just don't know. It may have the diaphragm to ensure the downstream pressure is handled, but once again, I don't know. There are many medical systems out there, and I really don't want to do much research into them.. I know what works, and your mileage may vary.

If you fly in an area where supplemental O2 is not often required, and you don't need it that often, and you are unfamiliar with its use, I think you should be extra careful to examine the capabilities of the system you choose.

I've been doing this for a long time, and I shake my head at some pilots that think it is simple to just get a bottle of welding gas (fine, as far as it goes) and just stick a hose in their mouth. It is a bit more complicated than that.

On Thursday, November 5, 2015 at 6:51:25 PM UTC-8, wrote:
Thanks for the advice, Mark. I'd love an EDS system. But here in the East we rarely go high enough to need oxygen, it seems that spending $1000 on a system is overkill for use once a year or so. Also, we have very few convenient places around here to refill, other than at "wave camp".

Do those medical regulators not have a diaphragm? You'd think that's necessary, in order to shut off (at least mostly) the flow coming from the high pressure cylinder? I was guessing they have a diaphragm-based pressure reduction followed by an orifice to set the flow rate, but I may be wrong. And perhaps even the diaphragm system would have some leakage through the high pressure side valve even when it's supposedly shut because the diaphragm senses that the output pressure is high. Then again, these regulators have an "off" position, on the same knob as the non-zero flow rates. If that is simply a zero-size orifice, wouldn't the pressure then build up dangerously in the low-pressure side of that device?

Agree with others... It's life support.
As evidenced in another thread, it's easy enough to get yourself into trouble on the "occasional 18,000' flight". 100% brain power when that happens is fairly important.
Jim

An Aerox system is cheaper than an EDS, maybe half the price. This is life support, as in LIFE, this epitomizes "pound foolish". If you really wanted to save the money on an O2 system, the much smarter choice is to stay at lower altitudes where you do not need it. This is not something to jury rig or kluge together on a budget with parts not designed for this use. Honestly!!!!

On Thursday, November 5, 2015 at 6:51:25 PM UTC-8, wrote:
Thanks for the advice, Mark. I'd love an EDS system. But here in the East we rarely go high enough to need oxygen, it seems that spending $1000 on a system is overkill for use once a year or so. Also, we have very few convenient places around here to refill, other than at "wave camp".

On Thursday, November 5, 2015 at 6:56:53 PM UTC-5, wrote:
On Thursday, November 5, 2015 at 6:19:34 PM UTC-5, wrote:
I'm looking for an inexpensive oxygen system for occasional flights up to 18,000 feet MSL. It seems easy to get a used medical type bottle with a regulator that includes a flow restriction built in. You can select, e.g., a 1 lpm flow rate right on the regulator. But, in a glider, you won't be able to reach this control when it is mounted behind the seat. My question is: with this type of regulator, if you add a flow valve and meter downstream, between that regulator and a cannula, and you open the flow on the medical regulator, but shut the added flow valve (unless and until you reach an altitude high enough to need oxygen), will the flow restrictor on the regulator protect the low-pressure hoses from excessive pressure, or will pressure build up enough to pop the hoses?

A side question is how to re-fill such a bottle.

Sounds a bit like do it yourself brain surgery.
Don't be a fool, buy proper equipment. This is a life support system.
UH

I can only second UH! I happened to attend a wave camp in the WVa where one participants decided to use a cheap medical mask on his A8A-regulator. Due to the cold, the mask shrank more than the hose and it fell out of the mask without him noticing. Although he correctly readjusted the flow according to altitude gain and the flow indicator showed 'green', the O2 was not getting to his mask. When it was getting late, we radioed the pilot and he was answering completely incoherent. We talked him into pulling the spoilers. He came down and landed with a huge headache. He stated that he had no recollection of being above 18,000'; the barograph (remember those?;-) )showed that he was well above the wave window's ceiling!
Sorry if I went off on a tangent here but it shows what happens if you skimp on vital equipment. You could end up paying the ultimate price!

Uli
AS

Agreed with most of the foregoing.

I'd be a lot more inclined to recommend aerox, if they didn't sell such complete garbage. For instance take a look he

http://wingsandwheels.com/oxygen-equ...ula-masks.html

That clear plastic mask is a total embarrassment, likely to break before first use (that's its best feature -- saves failure at 25K feet). The needle valve and flow meter assembly shown (the one with the right angle valve at the inlet) will almost certainly break on you too. Total rubbish. You guys at W&W ought to be ashamed to carry that stuff.

You can assemble a decent quality aerox system, but you have to pick and choose. Their regulators seem to be okay and the "glow meter" flow meters (see for instance @ Chief aircraft) seem to be rugged enough (well, two seasons and haven't broken mine yet). The blue silicone masks are okay, but seem exorbitantly expensive for what they are. You'll be annoyed when you spend almost $200 and the thing shows up with a tag that says "return to manufacturer by such and such a date for overhaul".

M&H has their issues too. I had a borrowed EDS system fail (wide open) on me in flight at 14,000. Man that was exciting. I talked to M&H about it the next day, they walked me through some basic trouble shooting, finally agreed that the unit was dead, and not repairable. They don't have any built in back up protection, even in the event that the battery just runs down. Really? On a life support system?

So yeah, I agree with the "go for quality -- it's your life" sentiments expressed by others here. Wish the manufacturers shared them.

Best regards,

Evan Ludeman / T8